Many types of working tools, such as chain saws, hedge trimmers, grass trimmers and other cutting machines operate in dusty environments. Also, the tools themselves are supplying surrounding air with lots of particles from the material that is tooled, e.g. wood, concrete, grass etc.
Traditionally, airfilters are used for cleaning intake air to the engine. However, these airfilters will soon be stopped up by larger or smaller particles and must therefore be exchanged and cleaned often, e.g. for a professional lumberjack working all day with a chain saw, typically once a day.
In order to reduce the need for maintenance of the air filter, it is desirable to clean the intake air before it reaches the air filter of the engine. Such cleaning of intake air can be achieved by centrifugal cleaning. For this reason, different types of deflection cleaners have been designed. In several cases deflection takes place at the inlet of a duct or similar, which debouches in a carburettor area, where the air filter and the carburettor is situated.
U.S. Pat. Nos. 4,716,860, 4,841,920, WO97/44582 and U.S. Pat. No. 5,720,243 show examples of such arrangements for cleaning of intake air. The arrangements shown in these documents utilize a fan wheel as a centrifuge for separating particles from the intake air, and a duct or an air nozzle with an inlet placed close to the fan wheel and an outlet placed near the air filter of the engine. As is shown in e.g. U.S. Pat. No. 5,720,243, the inlet of the air nozzle is placed adjacent to the fan wheel with a distance to the periphery of a surrounding fan housing. Since particles are thrown against the periphery of the fan housing due to the centrigual force, and since the inlet of the duct or air nozzle is placed adjacent to the fan wheel with a distance to the fan housing, the air that flows into the inlet of the air nozzle is substantially free from particles.
The prior art arrangements described above are relatively expensive to produce and to assemble in a hand-held motor-driven tool, and there is always a desire to produce and assemble tools as cost-effective as possible. Also, in the prior art arrangements there is a risk that a small opening or slot will exist between the fan housing and the air nozzle, after the air nozzle and the fan housing has been assembled, through which opening air may slip through. This may result in a pressure fall and turbulence in the air which would result in a less effective cleaning of the intake air. Therefore, there is a need to provide a motor-driven tool with an arrangement for cleaning of intake air which is effective in cleaning the intake air and at the same time cost-effective to produce and assemble.